Means for controlling electromagnets and solenoids.



L. L. TATUM.

MEANS FOR CONTROLLING ELECTROMAGNETS AND SOLENOIDS.

APPLICATION FILED JUNE 16, 1910. RENEWED MAR. 19, 1913.

1,077,319, Patented NOV.4,1913.

Illlllliiu N 0 UNITED STATES PATENT onnron.

LEWIS L. TA'I'UM, OF MILWAUKEE, WISCONSIN, ASSIGNOR TO THE CUTLER-HAMMER MFG. C0,, 01 MILWAUKEE, WISCONSIN, A CORPORATION OF WISCONSIN.

MEANS FOR CONTROLLING ELECTROMAGNETS AND SOLENOIDS.

Specification of Letters Patent.

Patented Nov. 4, 1913.

Application filed June 16, 1910, Serial No. 567,219. Renewed March 19, 1913. Serial No. 755,519.

To all whom it may concern.

Be it known that I, LEWIS L. TATUM, a citizen of the United States, residing at Milwaukee. in the county of Milwaukee and State of Wisconsin, have invented new anduseful Improvements in Means for Controlling Electromagnets and Solenoids, of which the following is a full, clear, concise, and exact description, reference being "had to the accompanying drawing, forming a part of this specification.

My invention relates to means for controlling electromagnets and solenoids.

It is the principal object of my invention to prevent the sticking of the plunger or armature of an electromagnetic winding when the same is deenergized.

Sticking of the plungers or armatures of elect-romagnets is commonly met with in practice. Particularly isthis condition met with in alternating current solenoids and magnets which are designed to prevent vibrating or chattering of the plungers or armaturcs thereof. In all alternating current solenoids which are designed to eliminate this chattering, it has been necessary to arrange the plunger or armature thereof to mechanically engage and seal with a relatively stationary magnetic part. In all such devices the current is apt to be cut off fromthe operating winding when the magnetic flux is at a maximum value, with the result that the residualmagnetism is sufficient to cause the plunger or armature to stick. The

plunger -or armature may stick for only a short time, or it may stick indefinitely. Such sticking of the plunger or armature is obviously objectionalie in practice, and it is to overcome such conditions that my invention is particularly directed.

While my invention is particularly applicable to alternating current magnets and solenoids, it should be understood that certain features thereof are also applicable to D. C. magnets and solenoids.-

For the purpose of more fully disclosing the nature and advantages of my invention I shall describe the embodiment thereof illustrated in the accompanying drawing. It should be understood, however, that my invention is capable of embodiment in various other fo'ms and is, therefore, not limited to the embodiment thereof illustrated in the accompanying drawing.

In the accompanying drawing, I have shown my invention exemplified in connection with an alternating current solenoid. The solenoid is diagrammatically illustrated asbcing providedwith a magnet frame 1, in which is mounted an alternating current winding 2. Within the windingQ, is ar ranged a longitudinally movable plunger 3 arranged to engage and seal with a stationary plug 4 carried by the magnet frame and projecting into the upper end of the Wind ing 2. In practice, the solenoid might be used to operate any desired mechanism. For the purpose of illustration, I have shown the plunger 3 as being provided with tail-rod 5 carrying a switch member 6 adapted when the Winding 2 is energized to be moved into engagement with contacts 7 and 8.

I have not illustrated any means for preventing the plunger 3 from vibrating or chattering, but it may be assumed that a shading coil has been provided in the stationary plug for this purpose. The function of a shading coil, as is well known in the art, is to set up an induced local flux around itself which is out of phase with the primary flux, and therefore, provides a limited amount of magnetic flux in the air gap during the time when the primary flux is passing through zero. This secondary fiux therefore tends to maintain the plunger in raised position during the reversals of the energizing current and thereby prevents chattering thereof. Where shading coils are used, in order to obtain a secondary flux of suflicient magnitude to be of any benefit without overheating the shading coil, it is necessary that the movable plunger be made to mechanically engage and seal with the stationary plug. As previously set forth, where such a mechanical engagement between the plunger and the stationary plug is provided for, the plunger will stick to the stationary plug, if current be cut off from the energizing winding when the magnetism happens to be at a high value.

According to my invention, I propose to prevent sticking of the solenoid plunger when the operating winding is deenergized, by passing through'said winding an alternating current of low potential insuiiiclent to maintain the plunger in its attracted position, but sufficient to overcome the residual magnetism to such an extent as to release the plunger. In other words, I propose to send through the operating winding an alternatinglcurrent of sufiicient value to demagnetize t e magnetic parts to a degree which will allow the plunger to drop and insuflicient to again attract the plunger. The shading coil will be of no avail when this weak current is sent through the operating winding, since the secondary flux produced thereby will be too small to hold the plunger against the weight of the load imposed thereon. The foregoing remarks, while dirooted to solenoids, are equally applicable to clectromagnets having movable armatures which seal with relatively stationary magnetic parts.

In the present instance, I secure the result above set forth, by providing a resistance 10, connected in parallel to the control switch 11. Assuming now, that current is supplied to the operating winding 2 from a single phase A, C. supply circuit 12-13, when the switch 11 is closed the winding 2 is energized causing the plunger 3 to be attracted, thereby moving the switch member 6 into engagement with its stationary contacts 7 and 8. When the switch 11 is opened to deenergize the winding 2, a circuit through said winding will be maintained through the resistance 10. The resistance 10 decreases the current flowing through the winding 2 to an amount sufficient to cause a change in polarity of the magnetic parts with each reversal of the exciting current, thereby releasing the plunger 3. This current, how ever, is insuflicient to cause the attraction of the plunger 3 after it has once been released. My invention thus provides a simple and efficient method which positively eliminates sticking of the plunger when its operating winding is denergized.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent, is:

1. The, combination with an eleetromagnet having a stationary pole-piece and a movable magnetically attracted part adapted to sea] with said pole-piece, of a control switch for said electromagnet and a resistance connected parallel to said control switch, said resistance being adapted when said control switch is opened, to reduce the current flowing through said electromagnet to an amount insufiicient to hold said magnetically attracted part, but suflicient to change the polarity of the magnetic parts upon each reversal thereof.

2. The combination with an alternating current solenoid having a stationary core and a movable plunger arranged to be ma gnetically attracted and to seal with said stationary core, of a switch for controlling the continuity of the circuit of the solenoid Winding and a resistance connected in par allel with said control switch to cause sulficient current topass through the solenoid winding to release said movable plunger when said switch is opened.

In witness whereof, I have hereunto subscribed my name in the presence of two witnesses. J

LEWIS L. TATUM.

Witnesses:

FRANK H. HUBBARD, GEORGE HAYNES. 

